Perpendicular magnetic recording has been developed in part to achieve higher recording density than is realized with longitudinal recording devices. A PMR write head (writer) typically has a main pole layer with a small surface area at an air bearing surface (ABS), and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through a main pole tip and enters a magnetic medium (disk) adjacent to the ABS. Magnetic flux is used to write a selected number of bits in the magnetic medium and typically returns to the main pole through two pathways including a trailing loop and a leading loop where both involve a shield structure. The trailing loop comprises a trailing shield structure at the ABS with a HMTS having a magnetization saturation value from 16 kiloGauss (kG) to 24 (kG), and a second trailing shield formed on a top surface and sides of the HMTS. The leading loop includes a leading shield with a front side at the ABS and that is connected to a return path proximate to the ABS. The return path extends to the back gap connection and enables magnetic flux in the leading loop pathway to return from the leading shield through the back gap connection to the main pole layer.
For both conventional (CMR) and shingle (SMR) magnetic recording, continuous improvement in storage area density is required for a PMR writer. A write head that can deliver or pack higher bits per inch (BPI) and higher tracks per inch (TPI) is essential to the area density improvement. An all wrapped around (AWA) shield design for a PMR write head is desired where the trailing shield is responsible for improving down track field gradient and BPI while side shields and a leading shield enhance the cross track field gradient and TPI as well as improve adjacent track erasure (ATE) also known as ATI.
In today's PMR writer designs, the HMTS formed on the write gap plays a key role in improving BPI. In particular, the HMTS attracts more main pole (MP) field to return from the soft underlayer (SUL) and thus enhance the field gradient in the down-track direction. The spacing (gap) between the HMTS and MP also controls the flux shunting of MP field and helps protect TPI and ATI. In the prior art, the HMTS is patterned only in a perpendicular direction that is orthogonal to the ABS so that there is no variation in down-track (DT) thickness as a function of cross-track position. Accordingly, further improvement in PMR writer performance is limited in terms of the tradeoff between enhancing TS return field, and improving side shield (SS) return field and ATI. Therefore, a new trailing shield design is needed to optimize the tradeoff between DT performance and cross-track (CT) performance for a PMR writer in hard disk drive (HDD).